Apparatus for cooling a continuous casting mould

ABSTRACT

The invention relates to an apparatus for cooling a continuous casting mould, comprising a cooling water supply conduit, an emergency cooling water supply conduit and a cooling water return conduit, all three conduits being joined to an overhead container which for its greatest part is filled with boiler feed water. At the upper part of said overhead container a space filled with a pressurized fluid is provided forming an elastic pressure cushion to protect the overhead container and all conduits from corrosion and boiler scale.

United States Patent 1191 Maurer Jan. 8, 1974 [54] APPARATUS FOR COOLING A 2,994,514 8/1961 Brown 165/107 x CONTINUOUS CASTING MQULD FOREIGN PATENTS OR APPLICATIONS [75] Inventor gust Mam", Ausma 486,277 11 1953 ltaly 164/128 [73] Assignee: Vereinigte Osterreichische Eisen-und stahlwelke Akfiellgeseuschafl, LinZ, Primary Examiner-Manuel A. Antonakas Austrla Attorney-Granville M. Brumbaugh et al. 22 P116111 DEC. 13, 1972 v 211 App]. No.: 207,167 [57] BSTRACT The invention relates to an apparatus for cooling a [30] Foreign Application Priority D t continuous casting mould, comprising a cooling water D80. 16 1970 Austria 11303/70 Supply conduit emergency 001mg water Supply conduit and a cooling water return conduit, all three 52 us. 01. 165/107 164/128 heihg Jhihed ah Overhead which 51 1111. c1 1522a 7/04 its greatest is filled with hiler feed Wateh At [58] Field 61 Search 165/11 106 107 the uPPer Part 0f Said overhead contain" a Space 165/137. 5 filled with a pressurized fluid is provided forming an m elastic pressure cushion to protect the overhead con- [56] References Cited .tainer and all conduits from corrosion and boiler UNITED STATES PATENTS scale 2,711,882 6/1955 Narbutovskih 165/107 X 8 Claims, 1 Drawing Figure 47 "flit? PATENTEU JAN 8 7 INVENTOR.

AUGUST MAURER l APPARATUS FOR OLHNG A CONTINUOUS CASTHNG MOULD The invention relates to an apparatus for cooling a continuous casting mould comprising a supply conduit for cooling water through which the cooling water is guided to the continuous cooling water supply conduit with a return valve, an emergency cooling water supply conduit with a return valve joined to an overhead container, said return valve of the emergency cooling water supply conduit being closed when the pump operates and being automatically opened when the pump fails, and a cooling water return conduit.

Cooling apparatus for continuous casting moulds have to be chosen with great care, in particular when steel is cast continuously. The cooling water temperature has to be regulated exactly and the formation of steam bubbles has to be avoided. When the coolant stream is interrupted, the wall of the continuous casting mould immediately melts through which may lead to explosions owing to the formation of detonating gas and to a damage of the continuous casting plant. Thus, care has to be taken that the coolant stream remains uninterrupted. It has already been proposed (Austrian Pat. No. 175 671) to arrange above the mould an open overhead container, which is connected with the continuous casting mould by means of a conduit containing a return valve. In cases of disturbances, eg, in case of a failure of the current supply, in the cooling water supply conduit a return valve is closed bypressure decrease and at the same time the return valve in the emergency cooling water supply conduit is opened so that from the overhead container cooling water may be guided into the continuous casting mould. in this known plant cleaned water is used which is supplied at a temperature of about 30 C from a further container to the continuous casting plant and is heated by about 6 C in running through. For continuous casting moulds of great dimensions, which are employed for casting broad steel slabs, the cooling water consumption will amount to from 120 to 1,000 m /h. When water of such a volume is circulated in an open circulatory system oxygen will be dissolved upon contact with air which causes a corrosion of the plant parts through which the cooling water flows and this, obviously, represents a disadvantage. Furthermore, temperature changes cause the water to evaporate which fact increases the hardness of the cooling water; this leads to undesired formations of boiler scale in the conduits and at the walls of the continuous casting mould. As a result it may happen that continuous casting moulds which are connected to an open cooling water circulatory system supplied with cleaned water, fail prematurely which reduces the output of the continuous casting machine. A further disadvantage of the known plant must be seen in the fact that the emergencyoperation can be maintained only for a relatively short period; it has to be terminated at the latest when the overhead container is empty. Thus, for servicing great continuous casting moulds for slabs overhead containers of very great dimensions have to be provided. In any case the duration of the emergency operation depends on the cooling water stored in the overhead container.

The invention is aimed at avoiding these difficulties and disadvantages and in an apparatus for cooling continuous casting moulds of the kind defined in the introduction resides in that the supply conduit and the return conduit for the cooling water are joined to the 2 overhead container which for its greatest part is filled with boiler feed water, the cooling water system and the overhead container being sealed against the atmosphere by means of a space filled with a pressurized medium such as gas or steam, representing an elastic pressure cushion.

Advantageously the pressure space in the upper part of the overhead container is filled with an inert gas, e.g., nitrogen, and connected via a conduit to a water tank which is preferably provided with a level regulating means and a fresh water supply conduit coacting therewith.

The pressure cushion is suitably adjustable to a pressure of 0.3 to 0.4 atmospheres gauge.

According to a preferred embodiment, in the cooling water container, in the area of the boiler feed water, a cylindrical vessel is provided which is closed at its lower end by a bottom and open at its upper end, and the cooling water return conduit ends in the vicinity of the bottom of the cylindrical vessel.

According to a further feature of the invention the level difference between the joining places of the emergency cooling water supply conduit at the cooling water container and at the continuous casting mould amounts to at least 5 m.

The cooling water container and the water tank are provided with-level regulating means and level regulating valves built in in respective water supply conduits.

For cooling the boiler feed water a heat exchanger is provided in the cooling water supply conduit.

In order that the invention may be more fully understood details of the invention shall now be described with reference to the accompanying drawing which schematically illustrates a coolant circulation system.

Numeral 1 denotes a continuous casting mould made of copper, to whose cooling jacket boiler feed water is guided by means of the cooling water supply conduit 2. Numeral 3 denotes the cooling water return conduit. The conduits 2 and 3 are joined to a closed cooling water container 4.

By a pump 5 the warmed cooling water is supplied from the cooling water container 4 into a heat exchanger 6 and cooled there. The coolant supply and drain conduits for the heat exchanger 6 are denoted with 7 and 8. Pressurized air or water may be used as coolant. Numeral 9 denotes a volume regulating valve in the coolant drain conduit 8 which valve is connected with a temperature regulating means 10 by means of an impulse line ill. The temperature regulating means 10 is in its turn connected via an impulse line 12 to the cooling water supply conduit 2 after the heat exchanger. By changing the coolant supply to the heat exchanger 6 the temperature of the cooling water supplied to the continuous casting mould 1 may be adjusted to a constant value. Numeral l3 is a device for measuring the throughflow which is joined to a measuring orifice 15 via an impulse line 14. Numeral 16 denotes a throughflow adjustment device which is connected via an impulse line 17 with a control valve 18. Numeral 1% denotes a return valve which is open when the pump 5 operates. Numeral 20 denotes a temperature measuring means for ascertaining the difference between the temperature when the water enters and the temperature when the water flows out of the mould, which means is joined to the cooling water conduits 2 and 3 via the impulse line 21.

The closed cooling water container 4 is primarily filled with boiler feed water, the maximum level being denoted with 22. Above, a pressure space 23 is situated which is suitably filled with an inert gas, e.g. nitrogen; thus, a protection is obtained for the mould and the conduits against corrosion and boiler scale; the gas pressure is adjusted to 0.3 to 0.4 atmospheres gauge, and the gas may be supplied through the conduit 24 via a closing member 25. Numeral 26 denotes asupply conduit for the boiler feed water; a return valve 27 and a level regulating valve 28 are built in in said conduit. The level regulating valve 28 is connected via an impulse line 29 with a level regulating means 30 arranged at the plane 22. During normal operation a water volume of about m is present in the cooling water container which volume is sufficient for cooling a continuous casting mould with a cross section of e.g., 2,000 X 300 mm and for a casting output of about 1.5 mt steel/- min.

Numerals 31,32 and 33 denote level alarm devices which are arranged on the planes 34, 35, 36 and start to function one after the other as soon as the water level in the cooling water container 4 sinks below the level 22. The area between the planes 22 and 34 is regarded as normal expansion or puffer area. if the water level sinks below the plane 34 the device 31 gives alarm and at the same time the boiler feed water is replenished via the conduit 26. In normal operation the water level does not sink below the level 34. In cases of disturbances or in an emergency operation the cooling water may sink to the level 35 where a further alarm is given by the device 32 so that casting may be inter rupted. When the water level sinks to the plane 36 the device 33 gives main alarm.

The pressure space 23 of the cooling water container 4 is connected by a connecting conduit 37 to a water tank 38 which is filled with clean water or drink water to the level 22; it may be refilled by a conduit 39 which contains a directly controlled (without current) level control valve 40 which is kinematically connected with a float 42 via a rod 41. Numeral 43 denotes a vent pipe containing a valve 44. The water tank 38 may be emptied by a conduit 45 comprising a valve 46. The vertical extension of thewater tank 38 or of the part of the connecting conduit 37 arranged in it is adjusted to the gas pressure present in the pressure space 23 of the container 4: during normal operation this gas pressure will displace the water column in the connecting conduit 37 to about the plane 47 so that also in case of pressure differences a gastight closure of the pressure space 23 remains intact; the boiler feed water in the cooling water container 4 thus cannot get into contact with air. When in the pressure space 23 over pressure is created, e.g., owing to the formation of steam, the water column in the connecting conduit 37 is displaced to the level 48 so that the steam bubbles in the water column of the water tank 38 ascend and condense; thus, it is impossible that too high a steam pressure in the pressure space 23 is created. If, on the other hand, for some reason or other, for example owing to the occurrance of a leakage in the cooling water system and at simultaneous failure of the supply boiler feed water, an underpressure originates in the pressure space 23, clean water or drinking water respectively, is sucked from the water tank 38 through the conduit 37 until normal operational conditions are created again. Numeral 49 denotes a free space in the water tank 38 the volume of which changes by level difierences.

A cylindrical vessel 50 is built in the cooling water container 4; said vessel has relatively a small diameter, it is closed at its lower end by a bottom 51 and open at its upper end, and it is communicatingly connected with the boiler feed water. The cooling water return conduit 3 is guided within this vessel 50 to the vicinity of the floor 51. The water flowing back from the mould 1 via the cooling water return conduit 3 contains small steam bubbles which form at the mould walls. These steam bubbles are condensed when the cooling water ascends in the water column in the vessel 50.

Numeral 52 denotes an emergency cooling water supply conduit which is connected with the lower end of the cooling water container 4; this conduit contains a return valve 53 which is closed in normal operation; said conduit is joined to the operational cooling water supply conduit 2 and thus leads to the mould l. The emergency cooling water supply conduit 52 enters into function in the case of a current failure, i.e. when the pump 5 stands still; in this case the return valve 19 closes automatically and the return valve 53 opens automatically. Numeral 54 denotes a conduit for emptying the cooling water container 4; said conduit contains a valve 55. The cooling water container 4 has to be arranged so high above the mould 1 that the level difference H between the level 56 determined by the cooling water outflow and the plane 57 determined by the cooling water entry amounts to at least 5 m, so that in case of disturbances the plant may safely continue to function and a natural cooling water circulation takes place.

During normal operation a closed forced circulation is maintained between the cooling water container 4 and the continuous casting mould by means of the cooling water pump 5; the cooling water flows through the cooling water supply conduit 2 to the mould and through the conduit 3 from the mould back into the cooling water container 4. In case of a current failure, i.e., during a standstill of the pump 5, the return valve 19 is closed by a pressure decrease in the conduit 2 and at the same time the return valve 53 is opened so that the cooling water is supplied from the cooling water container 4 via the emergency cooling water supply conduit 52 to the continuous casting mould 1. Experience has shown that such an emergency operation may be maintained for at least 20 minutes which suffices for casting that amount of steel which is present in a tundish above the mould, not shown, without disturbances. During the emergency operation the temperature of the cooling water in the continuous casting mould obviously increases from about 30 C to a maximum of about 1 10 C and the formation of steam increases as well. The cooling water containing hot steam bubbles gets via the cooling water return conduit 3 into the vessel 50 where it ascends by thermosyphon effect i.e., under formation of a natural cooling water circulation and is cooled; the steam bubbles condense thereby. In the degree in which the total cooling water amount taking part in the natural circulation is further heated and evaporated, the pressure in the pressure space 23 increases owing to the not condensed steam, until finally the water column present in the connecting conduit 37 is pressed down to the level 48 so that then steam is condensed in the clean water or drinking water of the water tank 38. If, with increasing cooling water evaporation the water level in the cooling water container 4 sinks too low for example below the level 34 fresh, cold boiler feed water is supplied into the system through the supply conduit 26 by operating the level control valve 28, unitl the steam condenses and the pressure in the pressure space 23 returns to the normal value of 0.3 to 0.4 atmospheres. Thus the continuous casting mould 1 cannot steam out and be destroyed. Owing to the level difference H, the water column in the cooling water container 4 and the gas pressure exerted on it, the water pressure in the emergency cooling water supply conduit 52 is greater at the entry into the mould 1 than at the exit into the conduit 3 so that the steam bubbles formed at the walls of the mould may more easily be guided off. A further advantage of the plant resides in that the apparatus is not subjected to the rigorous conditions for steam boilers because the gas pressure employed does not exceed 0.3 to 0.4 atmospheres gauge; the plant may also be operated with steam pressure but this is more expensive and makes the operation more complicated. Obviously, it is possible that several continuous casting moulds can be joined to a common cooling water container 4.

What is claimed is:

1. An apparatus for cooling a continuous casting mould comprising a casting mould a closed container,

the container being positioned above the casting mouldand being at least partially filled with cooling water, a pressurized inert gas in the container forming an elastic pressure cushion above the cooling water, a first supply conduit from the container to the casting mould, a return conduit from the casting mould to the container, pump means for supplying the cooling water in the container to the casting mould and returning the water from the casting mould to the container, flow regulating means for providing a predetermined amount of water to the casting mould, temperature regulating means for maintaining the temperature of the water in the casting mould at a predetermined temperature, a second supply conduit from the container to the casting mould, and valve means connected to the second supply conduit and adapted to be opened only when the pump fails, the container, conduits, and casting mould being sealed from the atmosphere forming a primary and emergency closed cooling circulation system.

2. The apparatus set forth in claim 1 further comprising a tank and a connecting conduit, the tank at least partially filled with water, having a water supply conduit and a water level regulating means, and the connecting conduit in communication with the water in the tank and the inert gas in the closed container.

3. The apparatus set forth in claim 1 wherein the inert gas is nitrogen.

4. The apparatus set forth in claim 1, wherein the pressure cushion is adjustable to a pressure of 0.3 to 0.4 atmospheres gauge.

5. The apparatus set forth in claim 1, wherein in said closed container, a cylindrical vessel is provided which is closed at its lower end by a bottom and open at its upper end, and the return conduit ends in the vicinity of said bottom within said cylindrical vessel.

6. The apparatus set forth in claim 1, wherein the second supply conduit is branched off the closed container and joined to the continuous casting mould at sites having a level difference between each other of at least 5 7. The apparatus set forth in claim 1, wherein the inert gas is connected via a connecting conduit to a water tank and each of said closed container and said water tank is provided with a level regulating means exchanger is provided in the first supply conduit.

@ 3 UNITED STATES- PATENT OFFICE v CERTIFICATE OF CORRECTION 3,783,937 Dated 197 Patent No Inventofls) August M urer It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

First page, Item [22], "Dec. 13, 1972" should'be --Dec. 13,

l97l--5 and I 001. 5, line 25, after "mould" insert a comma. cc rr n Signed and sealed this 10th day of September 197 (SEAL) Attes't:

McCOY M. GIBSON, I C. MARSHALL DANN Attesting Officer Commissioner of Patents 

1. An apparatus for cooling a continuous casting mould comprising a casting mould a closed container, the container being positioned above the casting mould and being at least partially filled with cooling water, a pressurized inert gas in the container forming an elastic pressure cushion above the cooling water, a first supply conduit from the container to the casting mould, a return conduit from the casting mould to the container, pump means for supplying the cooling water in the container to the casting mould and returning the water from the casting mould to the container, flow regulating means for providing a predetermined amount of water to the casting mould, temperature regulating means for maintaining the temperature of the water in the casting mould at a predetermined temperature, a second supply conduit from the container to the casting mould, and valve means connected to the second supply conduit and adapted to be opened only when the pump fails, the container, conduits, and casting mould being sealed from the atmosphere forming a primary and emergency closed cooling circulation system.
 2. The apparatus set forth in claim 1 further comprising a tank and a connecting conduit, the tank at least partially filled with water, having a water supply conduit and a water level regulating means, and the connecting conduit in communication with the water in the tank and the inert gas in the closed container.
 3. The apparatus set forth in claim 1 wherein the inert gas is nitrogen.
 4. The apparatus set forth in claim 1, wherein the pressure cushion is adjustable to a pressure of 0.3 to 0.4 atmospheres gauge.
 5. The apparatus set forth in claim 1, wherein in said closed container, a cylindrical vessel is provided which is closed at its lower end by a bottom and open at its upper end, and the return conduit ends in the vicinity of said bottom within said cylindrical vessel.
 6. The apparatus set forth in claim 1, wherein the second supply conduit is branched off the closed container and joined to the continuous casting mould at sites having a level difference between each other of at least 5 m.
 7. The apparatus set forth in claim 1, wherein the inert gas is connected via a connecting conduit to a water tank and each of said closed container and said water tank is provided with a level regulating means and a water supply conduit with a level regulating valve.
 8. The apparatus set forth in claim 1, wherein a heat exchanger is provided in the first supply conduit. 